To control high frequency wind noise upper than 1 kHz is important to ensure the comfort for a driver and passengers when vehicles cruise at high speed. Therefore the prediction method for high frequency wind noise inside a cabin has been required for development of a vehicle. This paper describes about the prediction method for high frequency wind noise from numerical simulation results. In this study, wind noise caused by airflow around a front pillar is predicted. We have predicted wind noise by visualizing noise sources and pressure fluctuation on vehicle surfaces in recent years. Although an inferior-to-superior relationship can be predicted from these results, it was difficult to estimate quantitative interior noise level. In this research, the SEA code is examined to predict such noise level. The SEA code has confirmed showing a qualitative and almost quantitative consistency of measured and calculated SPL at the head area of a front passenger seat.

In case that heat injury performance is analyzed with CFD, large calculations are required to solve heat and mass flow field inside the exhaust pipes, in the engine compartment and around vehicle body simultaneously. Since it spends much time for the generation of the analytic models and their solution by full CFD, such calculations are not practical to the industrial development of the vehicle in which many parameter studies on various conditions are required. Wherein, we suggest new method for prediction of the heat injury on exhaust systems, which is simplified with 1 dimensional models though the engine compartment flow is calculated with 3 dimensional calculations, i.e. CFD. Basic idea of this method is to divide exhaust systems into several elemental modules where heat transfer characteristics are given individually and to imitate actual systems by connecting them. Then 3D calculation is processed coupling heat and flow field with radiant filed outside exhaust systems. Above all, chemical reaction occurs in the catalytic converter is solved carefully to estimate heat production. This report introduces an overview of their 1-dimensional model and the calculation results.

Sunroof wind throb can generate annoyingly high sound-pressure levels (SPL) inside the vehicle cabin. In this study, several deflector configurations were installed to investigate this flow-acoustic coupled resonance phenomenon in passenger cars. In each condition, comparisons between the experimental results and numerical simulations were performed over a range of wind speeds to validate the capability of the PowerFLOW numerical simulation for wind throb prediction. Experiments were performed at the Suzuki full scale wind tunnel. One microphone in the cabin was set to record the pressure history and SPL. Flow around the sunroof was also measured by PIV. In both experiments and simulations, the following phenomena were observed. In case of strong wind throb, flow separates from the deflector and strong periodic vortices in the shear layer were observed. These vortices break down due to the impingement at the back-end of the sunroof and generate a strong peak noise in the cabin. In case of no wind throb, the periodic vortices were not observed resulting in a very weak peak with low SPL in the cabin. The deflector study shows that wind throb is a highly sensitive phenomenon where even a small geometry variation at the critical region can affect the phenomenon significantly. In this study, the same trend was obtained in the experimental results and simulations. It shows that the numerical simulation can be used for a priori predictions in the early stages of the vehicle design process.

Recently, CFD technology has become popular to the prediction of the engine cooling performance for the design of the automotive engine cooling systems. Particularly, the practical prediction of the cooling fan performance is one of the important issues. In the design phase of the vehicle development, combinations of multiple parameters are generally examined. Certainly, the unsteady calculations such as LES or LBM, which require high resolution of the space, give good accuracy meanwhile they spend much time for their executions so that they are not always practical. Therefore, the steady RANS coupling with MRF method is indispensable. However, it has been pointed out that, in case of complicated layout around the fan of an actual vehicle, the size of the MRF-region dominates predictive accuracy while the symmetry of the flow structure is taken account. Then, in this study, attracting on the discontinuity at the boundary surface of the MRF-region, authors found the method to determine adequate MRF-region to predict the fan performance in practical accuracy. This paper deals with the outline of the method and their applications.

The need for reliable CFD simulation tools is a key factor for today’s automotive industry, especially for what concerns aerodynamic design driven by critical factors such as the engine cooling system optimization and the reduction of drag forces, both limited by continuously changing stylistic constraints. The Ahmed body [1] is a simplified car model nowadays largely accepted as a test-case prototype of a modern passenger car because in its aerodynamic behavior is possible to recognize many of the typical features of a light duty vehicle. Several previous works have pointed out that the flow region which presents the major contribution to the overall aerodynamic drag, and which presents severe problems to numerical predictions and experimental studies as well, is the wake flow behind the vehicle model. In particular, a more exact simulation of the wake and separation process seems to be essential for the accuracy of drag predictions. In this paper a numerical investigation of flow around the Ahmed body, performed with the open-source CFD toolbox OpenFOAM®, is presented. Two different slant rear angle configurations have been considered and several RANS turbulence models, as well as different wall treatments, have been implemented on a hybrid unstructured computational grid. Pressure drag predictions and other flow features, especially in terms of flow structures and velocity field in the wake region, have been critically compared with the experimental data available in the literature and with some prior RANS-based numerical studies.

Boat-tails offer significant promise in reducing long haul heavy vehicle aerodynamic drag, and hence fuel consumption and greenhouse gas emissions. This paper presents results from a basic numerical and experimental investigation of drag coefficient reductions for various boat-tail configurations. The vehicle chosen is an arbitrary streamlined front end with a width to height ratio of 64%. No tractor to trailer gap is modeled. Approximate model scale is 12% and test Reynolds Number is ∼850,000. Experimental data and numerical simulations are presented for the zero yaw angle condition. For boat-tail angles where the flow remains largely attached a relationship is observed between drag reduction and the minimum boat-tail area. An optimum boat-tail angle (in the range of 15 degrees) is identified for 0 degrees yaw from both experimental and numerical data. For boat-tail angles greater than optimum a distinct increase in drag is observed in the experimental data, which is associated with flow separation. Comparison of experimental and numerical results show reasonable agreement for attached flow cases, and indicate a similar optimal boat-tail angle.

A typical cooling system of an engine relies on a water pump that circulates the coolant through the system. The pump is typically driven by the crankshaft through a mechanical link with engine starting. In order to reduce the friction and warm-up time of an engine, the clutch-type water pump (CWP) was applied in 2.0 liter diesel vehicle. The clutch-type water pump can force cooling water to supply into an engine by the operation of an electromagnetic clutch equipped as the inner part of pump system. The operation of CWP is decided by temperature of cooling water and engine oil. And, the control logic for an optimal operation of the clutch-type water pump was developed and applied in engine and vehicle tests. in this study, the warm-up time was measured with the conventional water pump and clutch-type water pump in engine tests. And the emission and the fuel consumption were evaluated under NEDC mode in vehicle tests. Also, tests were carried out at the various temperature conditions starting the operation of CWP. As the results, the application of CWP can improve the fuel consumption and CO 2 reduction by about 3%.

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia (NH 3 ) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and NH 3 slip reduction in the SCR system. This paper investigated NOx and NH 3 emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and O 2 for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm cannot estimate NH 3 absorbed on the catalyst Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated based on the analytic model for SCR system. The channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

We investigated the efficacy of fuel stratification in a pre-mixture of di-methyl ether (DME) and n-Butane, which have different auto-ignition characteristics, for reducing the pressure rise rate (PRR) of homogeneous charge compression ignition (HCCI) engines. A new chemical reaction model was created by mixing DME and n-Butane and compared to existing chemical reaction models to verify the effects. The rate of maximum pressure rise depends on mixture ratio. When DME was charged with stratification and n-butane was charged with homogeneity, the maximum PRR was the lowest. The calculations were performed using the SENKIN application of CHEMKIN-II.

Two centrifugal HVAC fan and casing geometries are experimentally and numerically investigated. Aerodynamic and acoustic measurements are performed at three operating conditions following an ISO standard procedure. Explicit and compressible CFD/CAA simulations based on the Lattice Boltzmann Method are performed for six configurations. From these simulations, flow information in term of pressure rise as a function of the mass flow rate and noise are obtained at the same time and compared to experiments. Additional post-processing is performed to have an insight on the origin and location of flow-induced noise sources.

Computational Fluid Dynamics (CFD) is today an important tool in the design process of fuel and energy efficient vehicles. Under hood Thermal Management (UTM) is one of the design fields which CFD has proven itself to be a very competitive design tool over other available tools and techniques. To simulate the under hood environment it is very important to predict cooling airflow accurately, and for this, it is very important to model all components in the cooling airflow path accurately. Important components are the heat exchangers, fan, grille-, and engine blockage. This paper has focused on CFD modeling of the fan using the most common fan model of the industry; Multiple Reference Frame (MRF). Several different aspects of this modeling strategy are examined that is of high importance to the CFD-engineer working with fan modeling. The finding of this paper is that the MRF model is highly capable of simulating fan airflow however some sensitivity are noted and documented. The model is very sensitive towards end-user working procedure. The CFD engineer working with this methodology in the under hood should be made aware of that the choice of reference frames and frozen position of the blade can have a very big impact on the simulated result.

In recent years, there have been increased concerns for the global warming and the exhaustion of resources caused by the heavy consumption of the fossil fuel. For this reason, biomass has been brought to great attention as a renewable source of energy to mitigate the situation. In this particular area, DME (dimethyl ether) fuel produced from biomass, biogas, and coal is expected to be useful as one of the eco-friendly synthetic fuel alternatives to petrodiesel. Diesel engine need fuel lubricity due to their severe condition (high pressure and temperature) but DME have low lubricity. In this study, we developed the analytic system for DME lubricity test which is pressurized chambered tester. Also we synthesized various of biodisel from 12 kinds of vegetable oil under base catalyst system. Oxygen compounds definitely contributed to the natural lubricity of fuel, biodiesel have ester group which is polar oxygenated functional group. After prepared test system and biodiesel as lubricant, we analyzed the lubricity of neat DME, neat biodiesels and DME-lubricant blended (100 ppm to 2000 ppm) fuel.

Small centrifugal and axial fans are used in automobile applications, as it is the case for HVAC systems for public transport. Typically, these fans are used to work at high speed (over 4000 rpm) and variable operation conditions, even at extreme off-design points. Flow instabilities, low efficiency and high levels of noise and vibrations appear in these machines due to these working characteristics and the need of low fabrication costs. However, lower noise levels are required today to improve the passengers comfort. Aiming to solve these problems, it is interesting to develop a computer application to predict the generated noise level (especially at the blade passing frequency BPF), which could be used during the design phase of the fans. In this paper, using Computational Fluid Dynamics (CFD) tools, the three-dimensional (3D) internal flow in a small squirrel-cage fan is computed unsteadily. Based upon the data acquired from the pressure fluctuations at the surfaces of 46 rotating blades and the volute tongue, the Ffowcs Williams-Hawkings analogy, which has been successfully applied in other types of turbomachines, is used to predict noise levels at the BPF. On the other hand, in order to validate the predicted numerical results, an experimental noise characterization in a semi-anechoic chamber using capacitive microphones and a real-time frequency analyzer is performed.

IHI has succeeded in development of a new generation Automated People Mover (APM). One of the features of this APM is the composite car body which enables stylish exterior, spacious cabin and light weight. This feature demanded the development of a new Heating, Ventilating, and Air-Conditioning (HVAC) system, which does not have any devices on the roof of the car, to avoid heavy weight on the composite body and to keep the cabin ceiling high for passenger comfort. Consequently we adopted a new HVAC flow system in which the air is supplied upwards from the bottom of the side windows while all the mechanical devices are placed under the floor. However, when the prototype was first designed, it caused congested flow channel due to its location and we had to have ducts that were too small. It was unexpectedly difficult to keep the space for HVAC system like in an ordinary layout. So at first, the prototype vehicle did not have enough HVAC performance due to lack of air flow. Therefore we performed full review of the duct system. We made desk analysis, duct model test, experiment on the prototype, and CFD simulation, for the improvement of the new HVAC flow system. Finally, we have established an excellent system with the new layout which has been validated on the prototype vehicle. In this paper, we describe the process of developing a new HVAC system, based on the results of actual measurement as well as CFD simulation.

Reductions of the side force and the connected yawing moment are of significance for driving stability under cross wind. This paper shows the suitable body shape under unsteady cross wind for reducing side force and yawing moment. Numerically, the shape changes such as rounded and/or cut off corners and patterned indented side surface under steady cross wind are evaluated, using k-ε model. The adequate shapes from the numerical data are experimentally validated under steady and unsteady cross wind in a wind tunnel. Flow structure and, side force and yawing moment are examined by High-speed PIV and a three-component load cell, respectively.

The need for simulating real-world behavior of automobiles has led to add more and more sophisticated models of various physical phenomena for being coupled together. This increases the number of parameters to be set and, consequently, the required knowledge of their relative importance for the solution and the theory behind them. Sensitivity and uncertainty analysis provides the knowledge of parameter importance. In this paper a thermal radiation solver is considered, that performs conduction calculations and receives heat transfer coefficient and fluid temperate at a thermal node. The equations of local, discrete, and transient sensitivities for the conjugate heat transfer model solved by the finite difference method are being derived for some parameters. In the past, formulations for the boundary element method and the finite element method have been published. This paper builds on the steady-state formulation published previously by the author. A numerical analysis on the stability of the solution matrix is being conducted. From those normalized sensitivity coefficients dimensionless uncertainty factors are calculated. On a simplified example the relative importance of the heat transfer modes at various locations are then investigated by those uncertainty factors.

Passenger cars represent the largest part of all means of personal transportation today. Thus, it is important to work towards reduced energy consumption of cars if a sustainable mobility is to be achieved. This involves many aspects of vehicle engineering; one of them being aerodynamics. This study focuses on aerodynamic drag and the contributions from the wheels at different cooling air flow configurations. Wheels and wheel housings are important for the overall aerodynamic drag on passenger cars. It has been shown that as much as 25% of the aerodynamic drag originates from these components. Therefore, it is desirable to understand the flow structures related to the wheels and wheel housings, and how they interact with other important flow regions. This paper presents an investigation of the effects of wheel designs on aerodynamic drag at different cooling air flow configurations on a sedan type passenger car. Comparisons between numerical simulations and wind tunnel measurements are made for some of the configurations as well. Several additional wheel configurations were investigated numerically to further investigate the flow structures at the front and rear wheels. The numerical results show that the effects of radial wheel covering varied noticeably with cooling air flow configuration. In two of the configurations this resulted in a net drag increase with closed cooling air inlets. The best configuration with closed cooling air inlets generated an overall drag reduction of 29 drag counts compared with the numerical baseline with open cooling air inlets. In addition to the obvious drag reduction of closing the cooling air inlets, the main reasons for the additional decrease was limiting the drag increase at the front stagnation region and positive interference effects along the underbody and vehicle base.

The main goal of this study is to obtain experimental data to develop adapted hydraulic and thermal wall functions used by industrial CFD codes. An experimental study, based on a test rig designed to reproduce realistic flow characteristics, has been conducted in order to explore velocity and temperature profiles. Hydraulic characterization of turbulent pipe flow was conducted over a Reynolds number range of 20 000 to 90 000, with three different test sections, presenting an increasing sand grain roughness. The three components of the flow velocity were measured, using laser Doppler velocimetry, and particle image velocimetry. The results obtained give access to turbulent quantities, to non-dimensional velocity profiles and to velocity defect in the boundary layer. These results are considered sufficient to cover the hydraulic requirements of an adequate wall-function related to surface roughness.

Hydrogen holds much promise as a source of energy that is at once abundant, clean, flexible, and secure. It is also environment friendly because it burns without producing carbon dioxide. Physical characteristics of hydrogen make it difficult to store in large quantities without taking up large amount of space. High pressure gas is a widely used storage mode for hydrogen fuel. Filling up process of a high pressure hydrogen tank should be reasonably short. The process should be designed so as to avoid high temperatures in the tank because of safety reasons. Numerical simulation can aid in optimizing the filling up process. The paper reports the numerical simulation of the filling up process of hydrogen tanks using computational fluid dynamics method. Real gas equations are solved to accurately simulate the process at the high temperature and pressure associated with the fast filling. Local temperature distribution in the tank is obtained at different durations of the fill. The numerical results obtained are validated with available experimental data.

A one-way coupled analysis was used to investigate both the unsteady aerodynamic forces on a simplified heavy-duty truck in strong wind gusts and their effects on its motion. The vehicle model for the dynamics simulation was extended to six degrees of freedom (6DoF). First, a transitional aerodynamics simulation was conducted for the simplified truck with a fixed vehicle attitude but subject to a sudden crosswind. Based on the visualized results of this aerodynamics simulation, flow phenomena generating transitional aerodynamic forces and moments are discussed, especially those acting in the vertical direction. While the truck was running into the crosswind region, the growth and breakdown of a large-scale vortex above the container generated a transitional behavior of aerodynamic lift and pitching moment. Next, time series of the six components of the aerodynamic forces and moments were input into the vehicle dynamics simulation. By comparing the results with those of a quasi-steady aerodynamics simulation, the effect of transitional aerodynamics on vertical motions was clarified, with the largest difference found in a rolling motion. Moreover, the effect of considering 6DoF was investigated by also conducting the vehicle dynamics simulation with 3DoF. The consideration of dynamics in the vertical direction changed the estimation of tire forces, which were related to a vertical load on the tire. Finally, the effects of considering 6DoF were also identified for horizontal motions.